Fuel cells are designed to transform fuel's chemical energy into electrical energy directly by electrochemistry reaction. Proton exchange membrane fuel cell (PEMFC) is one of the common systems due to high conversion efficiency and high degree of environmental friendliness.
In PEMFC systems, hydrogen fed into the anode can diffuse toward the catalyst on anode side via the gas diffusion layer and be catalyzed to dissociate into protons (H+) and electrons (e−) by Pt in the catalyst (H2→2H++2e−). Electrons flow to the cathode via external circuit and protons are transported into the catalyst on cathode side by the proton exchange membrane (PEM). In the cathode, water is generated by reduction reaction of protons, electrons and oxygen fed into the cathode (4H++4e−+O2→2H2O). PEMFC systems will not pollute the earth because the fuel is hydrogen and the products are water and heat (2H2+O2→2H2O).
PEM is key component in performance and life-cycle of PEMFC systems. Perfluorosulfonic acid (PFSA) ionmer membranes, such as Nafion® (DuPont), are preferred materials due to high proton conductivity and great service life (more than 60000 h). However, PFSA membranes have some disadvantages such as decreased proton conductivity caused by low water retention in high-temperature and low-humidity environment, limited performance in higher temperatures because of low glass transition temperature (Tg), high cost and environmental inadaptability. As a result, alternative PEM materials are under intense investigation.
Taiwan patent I527842 disclosed a polymer of fluorine-containing sulfonated poly(arylene ether)s which was synthesized by nucleophilic polycondensation of fluorine-containing monomers having 1 to 6 fluoro or trifluoromethyl groups and multiphenyl monomers. However, the fluorine-containing monomers may cause decreased hydrophilicity and conductivity of the polymer and disadvantageous to PEM performance in fuel cell.